Graft copolymers having improved phase binding between the graft base and the grafted-on polymer phase

ABSTRACT

Graft copolymers having improved phase binding between the graft base and the grafted-on polymer, are prepared from: 
     a) a grafted-on polymer phase containing one or more monomers from the group consisting of (meth)acrylates of alcohols having 1 to 10 carbon atoms, vinyl esters of saturated aliphatic carboxylic acids having 2 to 10 carbon atoms, olefins, vinyl halides, styrene and styrene derivatives, and 
     b) a peroxy group-containing copolymer phase containing from 0.01 to 20% by weight of an olefinically unsaturated peroxy compound of the general formula I or II ##STR1##  where R 1  is a chemical bond or a linear or branched alkyl chain having 1 to 10 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms, R 2  and R 3  are an alkyl group having 1 to 4 carbon atoms, R 4  is an alkyl group or an alkyl-substituted phenyl group having 3 to 12 carbon atoms, and R 5  is a cycloalkyl group having 3 to 12 carbon atoms, and from 80 to 99.9% by weight of one or more comonomers from the group consisting of the (meth)acrylates of alcohols having 1 to 10 carbon atoms, vinyl esters of saturated aliphatic carboxylic acids having 2 to 10 carbon atoms, olefins, vinylaromatic compounds, vinyl halides and/or vinyl ethers. 
     The graft copolymers are useful as binders in the textile industry as heat stable binders, as adhesives in plasters and as binders in emulsion paints.

This is a division, of application Ser. No. 967,662, filed Oct. 28, 1992now U.S. Pat. No. 5,304,609.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to graft copolymers having improved phase bindingbetween the graft base and the grafted-on polymer phase, to the peroxygroup-containing copolymers on which these are based, and tocopolymerizable peroxy monovinyl esters. The invention furthermorerelates to processes for the preparation of said polymers and peroxycompounds.

2. Background Art

Copolymerizable initiators offer interesting opportunities in thepreparation of novel polymeric materials. By means of such initiators,potential free-radical functions which function as defined anchor groupsin the preparation of graft and block copolymers, are introduced intopolymer chains. One area of application is, for example, the phasecoupling of incompatible polymers in core/shell latices during thepreparation thereof by the emulsion polymerization process.

Peroxy carbonates containing an allylic double bond and the use thereofas comonomers in copolymerization with further ethylenically unsaturatedmonomers are described in DE-A 2726008. German Patent 3420048 relates tocopolymers of vinyl acetate and peroxyallyl carbonates and the usethereof as sizing agents for glass fibers. It is disadvantageous thatthese allyl-functional peroxy carbonates only copolymerize very slowly,if at all, with other vinyl monomers.

EP-A 277608 (U.S. Pat. No. 4,879,347) and EP-A 279430 (U.S. Pat. No.4,839,432) describe copolymerizable peroxy carbonates containing (meth)acrylate and allyl ether functions as comonomers for improving the phasebinding in the preparation of polymer blends. The peroxy carbonate ispolymerized here with vinyl monomers in the presence of an ethylenecopolymer by the suspension polymerization process. On heating of themixture, coupling of the two polymer phases takes place via the peroxyfunctions. U.S. Pat. No. 4,923,956 describes a procedure which isanalogous to EP-A 279430, with the difference that propylene polymersare employed instead of the ethylene polymers. EP-A 307802 relates tomixtures of polypropylene, a further polymer and copolymer made from avinyl monomer and a peroxy carbonate containing an allyl ether or (meth)acrylate function; the phase binding thereof being improved by heatingto temperatures of from 200° to 300° C. EP-B 225091 describes allylether-substituted peroxy dicarbonates used as initiators for thepreparation of high-molecular-weight, branched VC polymers. Theabove-mentioned copolymerizable peroxy esters, in particular the allylcompounds, have the disadvantage of low reactivity on copolymerizationwith other vinyl monomers. Further more, said peroxy esters can onlyinitiate further free-radical reactions from temperatures ≧130° C. andare thus of no interest for emulsion polymerization.

The known methylstyrene-based peroxy compound discussed by W. C. Endstrain Kautschuk und Gummi, Kunststoffe 42(5), 414 (1989) has thedisadvantage that it cannot be copolymerized with many vinyl monomers,and further free-radical reactions are only initiated thermally fromtemperatures ≧160° C. The same applies to tert.-butyl-peroxy(p-(vinylbenzoyl) benzoates (I. Gupta, S. N. Gupta, D. C. Neckers, J.Polym. Sci.: Polym. Chem Ed. 20, 147 (1982), which only thermallyinitiate further free-radical reactions from T ≧100° C. and thus cannotbe employed for copolymerization by the emulsion polymerization process.

The object was therefore to provide olefinically unsaturated peroxycompounds which are copolymerizable with ethylenically unsaturatedmonomers whose peroxy group is retained during the copolymerization andwhose peroxy groups, after incorporation into the copolymer, are able toinitiate further free-radical polymerization reactions at temperatures≦100°. A further object was to provide these peroxy compound-containingcopolymers and the graft copolymers based on the peroxy group-containingcopolymers.

Surprisingly, we have found that this object is achieved by means ofperoxy monovinyl esters of aliphatic dicarboxylic acids and copolymersor graft copolymers containing these peroxy compounds.

SUMMARY OF THE INVENTION

The invention relates to peroxy monovinyl esters of aliphaticdicarboxylic acids having the general formula I or II ##STR2## where R¹is a chemical bond or a linear or branched alkyl chain having 1 to 10carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms; R² andR³ are an alkyl group having 1 to 4 carbon atoms, R⁴ is an alkyl groupor an alkyl-substituted phenyl group having 1 to 12 carbon atoms or acycloalkyl group having 3 to 12 carbon atoms, and R⁵ is a cycloalkylgroup having 3 to 12 carbon atoms. Examples of these are t-butylperoxymonovinyl esters, t-amylperoxy monovinyl esters, the cumylperoxymonovinyl esters and the pinylperoxy monovinyl esters of oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,suberic acid, azelaic acid and sebacic acid.

Preference is given to compounds of the formula I in which R¹ is(CH₂)_(n) where n=1 to 4 and n=8, R² and R⁴ are a methyl group, and R³is a methyl, ethyl or phenyl group; these compounds are thet-butylperoxy monovinyl esters, the t-amylperoxy monovinyl esters andthe cumylperoxy monovinyl esters of malonic acid, succinic acid,glutaric acid, adipic acid and sebacic acid.

Particular preference is given to compounds of the formula I in which R¹is (CH₂)_(n) where n is 2 to 4 and n=8, and R², R³ and R⁴ are a methylgroup; these compounds are the t-butylperoxy monovinyl esters ofsuccinic acid, glutaric acid, adipic acid and sebacic acid. Greatestpreference is given to t-butylperoxy monovinyl adipate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The peroxy monovinyl dicarboxylates according to the invention arepreferably prepared starting from the corresponding monovinyldicarboxylates of the general formula H₂ C═CH--O--CO--R¹ --COOH byesterification of the free acid group by means of the correspondingalkyl hydroperoxide of the general formula CR² R³ R⁴ --OOH or R⁵ ═CR⁴--OOH, where the radicals R¹, R², R³, R⁴ and R⁵ are as defined above.Synthetic routes starting from the corresponding monovinyl dicarboxylicanhydrides or dicarboxylic acid halides are also conceivable.

In a particularly preferred embodiment, the esterification is carriedout in the presence of dicyclohexylcarbodiimide (DCCD), the alkylhydroperoxide and DCCD each being employed in a molar ratio of from 1:1to 1:2, in each case based on the monovinyl dicarboxylate. In the mostpreferred embodiment, the monovinyl dicarboxylate, the alkylhydroperoxide and the dicyclohexylcarbodiimide are employed inapproximately equimolar ratios and reacted with one another at atemperature of from 0° to 40° C., if desired in the presence of an inertsolvent such as diethyl ether.

The olefinically unsaturated peroxy compounds according to the inventionare suitable for the preparation of copolymers which contain peroxidegroups and behave as "macroinitiators" in the block or graftcopolymerization. The free peroxide groups in the copolymer function asanchor groups in the graft copolymerization and thus improve the phasebinding of incompatible polymer phases, for example in core/shelllatices. However, the reaction conditions in the copolymerization forthe preparation of the peroxide-containing copolymers must be selectedso that the peroxide bond is not broken.

The invention furthermore relates to copolymers which contain the peroxymonovinyl esters of the formula I or II and to processes for theirpreparation. The peroxide group-containing copolymers contain between0.01 and 20% by weight of the olefinically unsaturated peroxy compoundaccording to the invention and from 80 to 99.9% by weight of one or morecomonomers from the group consisting of the (meth)acrylates of alcoholshaving 1 to 10 carbon atoms, vinyl esters of saturated aliphaticcarboxylic acids having 2 to 10 carbon atoms, olefins, vinylaromaticcompounds, vinyl halides and/or vinyl ethers, the data in % by weight ineach case being based on the total weight of the copolymer. The contentof peroxy compound is preferably from 0.01 to 10% by weight,particularly preferably between 0.01 and 5% by weight.

Preferred base monomers are selected from the group consisting of themethacrylates or acrylates of alcohols having 1 to 10 carbon atoms,methyl methacrylate, methyl acrylate, ethyl methacrylate, ethylacrylate, isopropyl methacrylate, isopropyl acrylate, tert.-butylacrylate, n-butyl acrylate and ethylhexyl acrylate; from the groupconsisting of the vinyl esters of saturated aliphatic carboxylic acidshaving 2 to 10 carbon atoms, vinyl acetate, isopropenyl acetate, vinylpropionate, vinyl laurate and vinyl esters of versatic^(R) acid having 9to 10 carbon atoms (vinyl esters of saturated α-branched monocarboxylicacids, commercial product from Shell); from the group consisting of theolefins, ethylene, propylene and 1,3-butadiene; from the groupconsisting of the vinyl halides, vinyl chloride, and styrene as thepreferred vinylaromatic compound.

If desired, the copolymers according to the invention may also contain,as base monomers, up to 10% by weight, based on the copolymer, ofethylenically unsaturated, functional comonomers. Examples of these aremono- or dicarboxylic acids such as methacrylic acid, acrylic acid orfumaric acid, and amides thereof; hydroxy-functional monomers such ashydroxyethyl acrylate, 2-hydroxypropyl acrylate or N-methylolacrylamide;sulphonate-functional monomers such as vinyl sulphonate or2-acrylamido-2-methylpropane sulphonate, and polyunsaturated monomerssuch as divinyl adipate.

Particular preference is given to copolymers containing one or morecomonomers from the group consisting of vinyl acetate, isopropenylacetate, vinyl propionate, vinyl laurate, vinyl chloride and/orethylene, and one or more olefinically unsaturated peroxy compoundsselected from the group consisting of the t-butylperoxy, t-amyl-peroxyand cumylperoxy monovinyl esters of malonic acid, succinic acid,glutaric acid and/or adipic acid. Greatest preference is given tocopolymers containing from 0 to 50% by weight of ethylene, from at least50% by weight of vinyl acetate and from 0.01 to 5% by weight oft-butylperoxy monovinyl adipate, the data in % by weight being based onthe total weight of the copolymer and adding up to 100% by weight.

The peroxy group-containing copolymers are prepared by free-radicalpolymerization in bulk, in solution, in suspension or in emulsion. Ofsaid processes, emulsion polymerization is the preferred variant. Thepolymerization can be carried out batchwise or continuously, with orwithout use of seed latices, with initial introduction of all or someconstituents of the reaction mixture or with partial initialintroduction and subsequent metering in of the or some constituents ofthe reaction mixture, or by the metering process without any initialintroduction. All meterings are preferably carried out at the rate ofconsumption of the respective components.

The polymerization is initiated by free-radical formers in a temperaturerange of from 0° to 80° C., since significant decomposition if theperoxy groups in the copolymer occurs at higher temperature. Thepolymerization is preferably carried out at temperatures up to 70° C.

In the case of the preferred emulsion polymerization, the initiation iseffected by means of water-soluble free-radical formers, which arepreferably employed in amounts of from 0.01 to 3.0% by weight, based onthe total weight of the monomers. Examples of these are ammonium andpotassium persulphate and peroxodisulphate; hydrogen peroxide; and azocompounds such as azobisisobutyronitrile or azobiscyanovaleric acid. Ifthe water-soluble free-radical former has a greater oxidation potentialthan the copolymerizable peroxide of the formula (I) or (II), forexample in the case of t-butylhydroperoxide, potassium peroxodisulphate,sodium peroxodisulphate and ammonium peroxodisulphate, the formation offree radicals can be accelerated at lower temperatures with the aid ofreducing agents.

Dispersants which can be employed are all emulsifiers and protectivecolloids usually used in emulsion polymerization. From 1 to 6% byweight, based on the total weight of the monomers, of emulsifier arepreferably employed. Examples of suitable compounds are anionic tensidessuch as alkyl sulphates having a chain length of from 8 to 18 carbonatoms; alkyl and alkylaryl ether sulphates having 8 to 18 carbon atomsin the hydrophobic radical and up to 40 ethylene oxide or propyleneoxide units; alkyl or alkylaryl sulphonates having 8 to 18 carbon atomsand esters and monoesters of sulphosuccinic acid with monohydricalcohols or alkylphenols. Examples of suitable non-ionic tensides arealkyl polyglycol ethers or alkylaryl polyglycol ethers having 8 to 40ethylene oxide units.

If desired, protective colloids may be employed, preferably in amountsof up to 15% by weight, based on the total weight of the monomers.Examples of these are vinyl alcohol-vinyl acetate copolymers containingfrom 80% to 100 mol % of vinyl alcohol units, polyvinylpyrrolidoneshaving a molecular weight of from 5000 to 400,000, andhydroxyethylcelluloses having a degree of substitution in the range offrom 1.5 to 3.

The pH range desired for the polymerization, which is generally between2.5 and 10, preferably between 3 and 8, may be established in a knownmanner by acids, bases or conventional buffer salts such as alkali metalphosphates or alkali metal carbonates. In order to adjust the molecularweight, the regulators usually used, for example mercaptans, aldehydesand chlorinated hydrocarbons, can be added during the polymerization.

The peroxide-containing copolymers are suitable as the graft base forthe preparation of graft copolymers, block copolymers and core/shelldispersion particles having improved phase binding between the polymerphases.

The invention furthermore relates to graft copolymers prepared from

a) a grafted-on polymer phase containing one or more monomers from thegroup consisting of (meth) acrylates of alcohols having 1 to 10 carbonatoms, vinyl esters of saturated aliphatic carboxylic acids having 2 to10 carbon atoms, olefins, vinyl halides, styrene and styrenederivatives, and

b) a peroxy group-containing copolymer phase containing from 0.01 to 20%by weight of the olefinically unsaturated peroxy compound according tothe invention and from 80 to 99.9% by weight of one or more comonomersfrom the group consisting of the (meth)acrylates of alcohols having 1 to10 carbon atoms, vinyl esters of saturated aliphatic carboxylic acidhaving 2 to 10 carbom atoms, olefins, vinylaromatic compounds, vinylhalides and/or vinyl ethers.

Preferred monomers of the graft monomer phase from the group consistingof (meth)acrylates of alcohols having 1 to 10 carbon atoms are methylmethacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate,isopropyl methacrylate, isopropyl acrylate, t-butyl acrylate, n-butylacrylate and ethylhexyl acrylate. Preferred vinyl esters of saturatedaliphatic carboxylic acids having 2 to 10 carbon atoms are vinylacetate, vinyl propionate and vinyl laurate. Preferred olefins areethylene and propylene. The preferred vinyl halide employed is vinylchloride. Particular preference is given to styrene and methylmethacrylate. In addition, the graft monomer phase may, if desired, alsocontain up to 10% by weight, based on the graft monomer phase, of theabove-mentioned ethylenically unsaturated, functional comonomers.

Preferred graft copolymers are those prepared from a graft basecontaining one or more comonomers from the group consisting of vinylacetate, isopropenyl acetate, vinyl propionate, vinyl laurate, vinylchloride and/or ethylene and containing from 0.01 to 10% by weight ofone or more olefinically unsaturated peroxy compounds from the groupconsisting of t-butylperoxy, t-amylperoxy and cumylperoxy monovinylesters of malonic acid, succinic acid, glutaric acid and/or adipic acid,and a grafted-on polymer phase made from (meth)acrylates of alcoholshaving 1 to 10 carbon atoms, vinyl esters of saturated aliphaticcarboxylic acids having 2 to 10 carbon atoms, vinyl halides, styreneand/or styrene derivatives.

Particular preference is given to graft copolymers prepared from a graftbase containing from 0 to 50% by weight of ethylene, from 50 to 100% byweight of vinyl acetate and from 0.01 to 5% by weight of t-butylperoxymonovinyl adipate, and a grafted-on polymer phase containing styrene ormethyl methacrylate.

The grafting can be carried out in bulk, solution, suspension oremulsion. It is preferably carried out by the emulsion polymerizationprocess. For the graft copolymerization, the peroxide-containingcopolymer is initially introduced, preferably in the form of a seedlatex. The graft monomer phase can be initially introduced or meteredin, for example as a preemulsion. The amount of graft monomer added isadjusted so that between 1 and 99% by weight of these monomer units arepresent in the finished graft product.

The graft copolymerization is carried out at temperatures ≧80° C.,preferably ≧90° C., without further addition of initiators, since theperoxide-containing copolymers, as macroinitiators, initiate the graftreaction. The graft copolymerization is preferably carried out withaddition of from 0.1 to 5.0% by weight of emulsifier, based on the totalweight of the graft copolymer.

The graft copolymer latex can be further worked up, for example by spraydrying, roller drying or by coagulation with subsequent drying.

The graft copolymer latices are suitable for use as binders in thetextiles sector (nonwovens), as heat stable binders, for example incoatings for roof sheeting, as adhesives in plasters and as binders inemulsion paints. Graft copolymer resins obtained by coagulation or spraydrying are suitable as impact modifiers in plastics, as phase promotersin polymer blends, as low profile additives in UP resins and for use asthermoplastic elastomers.

The examples below serve to illustrate the invention in greater detail:

EXAMPLE 1

6.1 g (29.56 mmol) of dicyclohexylcarbodiimide were dissolved in 14 mlof diethyl ether in a 250 ml flask fitted with magnetic stirrer,dropping funnel and internal thermometer. 5.0 g (29.04 mmol) ofmonovinyl adipate were dissolved in 30 ml of diethyl ether and addedslowly with vigorous stirring. After only a short time, a white,flocculant precipitate had formed. As soon as the addition of monovinyladipate was complete, the mixture was cooled to below 5° C., and theresultant precipitate was dissolved by addition of 20 ml ofdichloromethane. 4.4 g (29.04 mmol) of t-butyl hydroperoxide were thenslowly added dropwise, and the batch was subsequently stirred for 5hours at temperatures below 5° C. and left to stand overnight at lowtemperatures. For work-up, the mixture was filtered through a suctionfilter. The residue was washed with a little dichloromethane, and theresultant clear solution was evaporated on a rotary evaporator, giving aclear liquid which decomposes at temperatures above 60° C.

¹ H-NMR (CDCl₃): 1.320 ppm, s, 9H; 1.705 ppm, m, 4H; 2.394 ppm, m, 4H;4.574 ppm, m, 1H; 4.877 ppm, m, 1H; 7.200 ppm, m, 1H.

EXAMPLE 2

Analogously to Example 1, 6.1 g (29.56 mmol) of dicyclohexylcarbodiimidewere dissolved in 14 ml of diethyl ether in a 250 ml flask. 6.66 g(29.04 mmol) of monovinyl sebacate were dissolved in about 30 ml ofdiethyl ether and slowly added dropwise with vigorous stirring. Thereaction was carried out precisely by the method described in Example 1,giving a clear liquid which solidifies at temperatures below 0° C. anddecomposes above 60° C.

¹ H-NMR (CDCl₃): 1.1-1.4 ppm, m, 17H, 1.51-1.73 ppm, m, 4H, 2.36-2.51ppm, m, 4H, 4.573 ppm, m, 1H, 4.879 ppm, m, 1H, 7.15-7.3 ppm, m, 1H.

EXAMPLE 3

Analogously to Example 1, 6.1 g (29.56 mmol) of dicyclohexylcarbodiimidewere dissolved in 14 ml of diethyl ether in a 250 ml flask. 4.62 g(29.04 mmol) of monovinyl glutarate were dissolved in about 30 ml ofdiethyl ether and slowly added dropwise with vigorous stirring. Thereaction was carried out precisely by the method described in Example 1,giving a clear liquid which decomposes at temperatures above 60° C.

¹ H-NMR (CDCl₃): 1.32 ppm, s, 9H, 1.95-2.07 ppm, m, 2H, 2.43-2.56 ppm,m, 4H, 4.571 ppm, m, 1H, 4.875 ppm, m, 1H, 7.15-7.3 ppm, m, 1H.

EXAMPLE 4

First, four solutions were prepared: 1. Initiator solution: 0.45 part byweight of potassium persulphate was dissolved in 14.6 parts by weight ofwater. 2. Monomers: 0.4 part by weight of divinyl adipate was dissolvedin 84.9 parts by weight of vinyl acetate. 3. Preemulsion: 0.8 part byweight of Na 2-acrylamido-2-methylpropanesulphonate and 2.2 parts byweight of a diisohexylsulphosuccinate (Aerosol MA 80 from Cyanamid) wereemulsified in 40 parts by weight of water. 4. Peroxide solution: 1.95parts by weight of t-butylperoxy monovinyl adipate (Example 1) weredissolved in 1.95 parts by weight of vinyl acetate.

9.75 parts by weight of vinyl acetate, 0.05 part by weight of divinyladipate, 0.25 part by weight of vinyl sulphonate, 0.515 part by weightof diisohexylsulphosuccinate (Aerosol MA 80 from Cyanamid) and 0.125part by weight of potassium persulphate were introduced into 87 parts byweight of water in a stirred autoclave, the mixture was warmed to 70°C., and the autoclave was charged with 80 bar of ethylene. When thetemperature equilibrium had been reached, the above-described solutions1 to 3 were metered in. The metering rates were selected to correspondto a metering time of 5 hours in the case of the monomers (2.) and ametering time of 6 hours in the case of the initiator (1.) and thepreemulsion (3.). When the metering of the monomers (2.) was complete,the peroxide solution (4.) was metered in over the course of one hour.

A finely dispersed dispersion having a solids content of 46% by weightand a monomodal particle size distribution, with the mean particle sizebeing 168 nm, resulted. The copolymer had an ethylene content of 41% byweight and an active oxygen content of 0.085%. The glass transitiontemperature of the polymer resin (DSC) was -21° C., and its K value(measured in tetrahydrofuran, THF) was 40.1.

EXAMPLE 5

The procedure was analogous to Example 4, with the difference thatt-butylperoxy monovinyl adipate was metered in together with the vinylacetate phase over the entire reaction time. To this end, threesolutions were prepared: 1. Initiator solution: 0.45 part by weight ofpotassium persulphate was dissolved in 14.6 parts by weight of water. 2.Monomers: 0.4 part by weight of divinyl adipate and 1.95 parts by weightof t-butylperoxy monovinyl adipate (Example 1) were dissolved in 86.8parts by weight of vinyl acetate. 3. Preemulsion: 0.8 part by weight ofNa 2-acrylamido-2-methylpropane-sulphonate and 2.2 parts by weight of adiisohexylsulphosuccinate (Aerosol MA 80 from Cyanamid) were emulsifiedin 40 parts by weight of water.

9.75 parts by weight of vinyl acetate, 0.05 part by weight of divinyladipate, 0.25 part by weight of vinyl sulphonate, 0.515 part by weightof a diisohexylsulphosuccinate (Aersol MA 80 from Cyanamid) and 0.125part by weight of potassium persulphate were introduced into 87 parts byweight of water in a stirred autoclave, the mixture was warmed to 70°C., and the autoclave was charged with 80 bar of ethylene. When thetemperature equilibrium had been reached, the above-described solutions1 to 3 were metered in. The metering rates were selected to correspondto a metering time of 6 hours.

A finely dispersed dispersion having a solids content of 47.6% by weightand a monomodal particle size distribution, with the mean particle sizebeing 179 nm, resulted. The copolymer had an ethylene content of 31% byweight and an active oxygen content of 0.266%. The glass transitiontemperature of the polymer resin (DSC) was -16° C., and its K value(measured in tetrahydrofuran, THF) was 40.3.

EXAMPLE 6

For the graft polymerization, 10 parts by weight of the peroxidegroup-containing copolymer from Example 4 in the form of a 6% strengthaqueous dispersion were introduced into a polymerization reactortogether with 0.005 part by weight of iron(II) ammoniumsulphate, themixture was heated to 90° C., and a preemulsion comprising 89.55 partsby weight of styrene, 0.45 part by weight of acrylic acid and 2 parts byweight of Aerosol MA in 45 parts by weight of water was metered in withstirring over a period of 2 hours. When the metering was complete, thegraft polymerization was completed at 93° C., giving a 39.5% strengthpolymer dispersion having a residual monomer content of 1.3% by weightand a mean particle size of 330 nm with a narrow, monomodal particlesize distribution. The K value of the resin was 65.1, and the insolublecontent in ethyl acetate was 29.7% by weight.

EXAMPLE 7

The procedure was analogous to Example 6, with the difference that 20parts by weight of the peroxide group-containing copolymer from Example5 were initially introduced in the form of an 11% strength aqueousdispersion, and 79.6 parts by weight of styrene, 0.4 part by weight ofacrylic acid and 1.4 parts by weight of Aerosol MA in 40 parts by weightof water were metered in, giving a 42.6% strength polymer dispersionhaving a residual monomer content of 0.78% by weight and a mean particlesize of 289 nm with a narrow, monomodal particle size distribution. TheK value of the polymer resin was 61.1, and the insoluble content inethyl acetate was 27.8% by weight.

EXAMPLE 8

The procedure was analogous to Example 6, with the difference that 90parts by weight of the peroxide group-containing copolymer from Example3 were initially introduced in the form of a 36% strength aqueousdispersion, and 9.95 parts by weight of styrene, 0.05 part by weight ofacrylic acid and 0.1 part by weight of Aerosol MA in 5 parts by weightof water were metered in, giving a 43% strength polymer dispersionhaving a residual monomer content of 0.26% by weight and a mean particlesize of 195 nm with a narrow, monomodal particle size distribution. TheK value of the resin was 42.1.

COMPARATIVE EXAMPLE 1

A copolymer was prepared analogously to Example 5, but not-butylperoxymonovinyl adipate was copolymerized. To this end, threesolutions were prepared:

1. Initiator solution: 0.45 part by weight of potassium persulphate wasdissolved in 14.6 parts by weight of water. 2. Monomers: 0.4 part byweight of divinyl adipate was dissolved in 88.8 parts by weight of vinylacetate. 3. Preemulsion: 0.8 part by weight of Na2-acrylamido-2-methylpropanesulphonate and 2.2 parts by weight of adiisohexylsulphosuccinate (Aerosol MA 80 from Cyanamid) were emulsifiedin 40 parts by weight of water.

9.75 parts by weight of vinyl acetate, 0.05 part by weight of divinyladipate, 0.25 part by weight of vinyl sulphonate, 0.515 part by weightof a diisohexylsulphosuccinate (Aerosol MA 80 from Cyanamid) and 0.125part by weight of potassium persulphate were introduced into 87 parts byweight of water in a stirred autoclave, the mixture was warmed to 70°C., and the autoclave was charged with 80 bar of ethylene. When thetemperature equilibrium had been reached, the above-described solutions1 to 3 were metered in. The metering rates were selected to correspondto a metering time of 6 hours.

A finely dispersed dispersion having a solids content of 43% by weightand a monomodal particle size distribution, the mean particle size being178 nm, resulted. The copolymer had an ethylene content of 36% by weightand an active oxygen content of 0%. The glass transition temperature ofthe polymer resin (DSC) was -25.4° C., and its K value (measured intetrahydrofuran, THF) was 39.4.

COMPARATIVE EXAMPLE 2

The procedure was analogous to Example 6, but the graft base initiallyintroduced comprised 10 parts by weight of the copolymer fromComparative Example 1 in the form of a 6% strength dispersion. In orderto initiate the graft reaction, an amount of initiator which wasequivalent to the peroxide groups of the copolymer from Example 4,namely 0.516 part by weight of t-butylperoxy pivalate and 0.174 part byweight of t-butylperoxy 2-ethylhexanoate, was metered into thepreemulsion together with 89.55 parts by weight of styrene, 0.45 part byweight of acrylic acid and 2.0 parts by weight of Aerosol MA in 40 partsby weight of water, giving a 41.8% strength polymer dispersion having aresidual monomer content of 0.78% by weight and a mean particle size of368 nm with a broad monomodal particle size distribution. The K value ofthe polymer resin was 50.2, and the insoluble content in ethyl acetatewas 2.5% by weight.

COMPARATIVE EXAMPLE 3

The procedure was analogous to Example 7, but the graft base initiallyintroduced comprised 20 parts by weight of the copolymer fromComparative Example 1 in the form of a 12% strength dispersion. In orderto initiate the graft reaction, an amount of initiator which wasequivalent to the peroxide groups of the copolymer from Example 5,namely 0.516 part by weight of t-butylperoxy pivalate and 0.174 part byweight of t-butylperoxy 2-ethylhexanoate, was metered into thepreemulsion together with 79.6 parts by weight of styrene, 0.40 part byweight of acrylic acid and 1.40 parts by weight of Aerosol MA in 30parts by weight of water, giving a 44.0% strength polymer dispersionhaving a residual monomer content of 0.57% by weight and a mean particlesize of 310 nm with a narrow, monomodal particle size distribution. TheK value of the polymer resin was 51.6, and the insoluble content inethyl acetate was 8.8% by weight.

It is clear from Examples 6 and 7 and Comparative Examples 2 and 3 thatthe molecular weight (see K value) of the graft polymers in the case ofgrafting onto the peroxide-containing copolymers ("macroinitiators") wassignificantly increased. The ethyl acetate-insoluble content of thegraft products is also significantly increased in the case of theperoxide-containing products and confirms the improved coupling of thepolystyrene phase to the EVAc phase.

What is claimed is:
 1. Peroxy group-containing copolymers containingfrom 0.01 to 20% by weight of peroxy monovinyl esters of the formula Ior II ##STR3## wherein R¹ is a chemical bond or a linear or branchedalkyl chain having 1 to 10 carbon atoms or a cycloalkyl group having 3to 10 carbon atoms, R² and R³ are an alkyl group having 1 to 4 carbonatoms, R⁴ is an alkyl group or an alkyl-substituted phenyl group having1 to 12 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms,and R⁵ is a cycloalkyl group having 3 to 12 carbon atoms and from 80 to99% by weight of at least one comonomer selected from the groupconsisting of the (meth)acrylates of alcohols having 1 to 10 carbonatoms, vinyl esters of saturated aliphatic carboxylic acids having 2 to10 carbon atoms, olefins, vinylaromatic compounds, vinyl halides andvinyl ethers.
 2. Peroxy group-containing copolymers according to claim1, wherein the copolymers contain from 0.01 to 20% by weight of peroxymonovinyl esters of the formula I or II and from 80 to 99.9% by weightof at least one comonomer selected from the group consisting of vinylacetate, isopropenyl acetate, vinyl propionate, vinyl laurate, vinylchloride and/or ethylene.
 3. Peroxy group containing copolymersaccording to claim 1 wherein the copolymers are composed of from 0 to50% by weight of ethylene, from at least 50% by weight of vinyl acetateand from 0.01 to 5% by weight of t-butylperoxy monovinyl adipate.